To adapt the steering wheel position to the seating position of the driver of a motor vehicle, steering columns are known in the prior art in which the steering wheel, mounted on the rear end of the steering spindle, can be positioned in the vehicle interior via a length adjustment in the direction of the steering column longitudinal axis.
The length adjustability is achieved in that the adjustment unit, which comprises the steering spindle mounted rotatably about the longitudinal axis in a casing tube, is displaceable telescopically in the longitudinal direction relative to the support unit, which forms a holder of the steering column connected fixedly to the vehicle body. By means of a releasable clamping device, the adjustment device can be secured, i.e. fixed releasably, in different length positions of the adjustment travel relative to the support unit, in order to lock the respective steering wheel position. A stop device ensures that in normal operation, the adjustment travel of the adjustment unit relative to the support unit is limited, in order to set the steering wheel position in the direction of the longitudinal axis. Here, a stop element, mounted on the support element and protruding into the passage cross-section of the adjustment unit, forms an end stop which the adjustment unit meets when it is moved longitudinally forward relative to the support unit, i.e. retracted, in relation to the direction of travel of the vehicle. In this way, the adjustment unit is blocked in the maximally retracted or shortened adjustment position, and cannot be moved further manually.
As an effective measure for improving occupant safety on a vehicle collision, known as a crash or vehicle frontal impact, in which the driver hits a steering wheel at high speed, it is known to configure the steering column so as to be collapsible in the longitudinal direction when a high force is exerted on the steering wheel which exceeds a limit value only occurring in a crash. In order to allow a controlled braking of a body hitting the steering wheel when the adjustment unit is in the maximally retracted or shortened adjustment position, i.e. in the end position limited by the stop element in the blocking position, it is known that the stop element is brought out of the blocking position into a release position in which the adjustment unit can be moved further in the direction of the longitudinal axis than the above-mentioned end position, i.e. can be retracted. In this way, an additional movement travel is provided for the adjustment unit which can be used for controlled energy absorption in the event of a crash.
A steering column with such a stop device is described for example in DE 10 2011 056 351 A1. This has a stop element which is connected to a control lever of a clamping device for fixing the adjustment unit in the support unit. In the open state of the clamping device, the stop element is in the blocking position so that the adjustment unit can be retracted forward only as far as the stop in order to set the steering wheel position. When the control lever is pivoted to fix the clamping device, the stop element is moved into the release position so that in the event of a crash, the adjustment unit can be moved further forward in the longitudinal direction. It is advantageous here that when the steering column is fixed, an extended adjustment travel is available for braking the adjustment unit. The disadvantage with the coupling of the stop element to the clamping device, however, is that then the additional adjustment travel is only released with certainty if the control lever has actually been pivoted sufficiently far. Also, the naturally frequent actuation of the clamping device entails actuation of the stop device each time, which can lead to wear and deterioration in function.
Thus a need exists for a steering column with improved actuation of a stop device.